1. Technical Field
The present invention relates to methods and related apparatus for automatically and effectively isolating ruptures in fluid piping systems without the need for shutdown or manual assistance, thereby allowing such piping systems to continue operating during the detection and isolation of system ruptures.
2. Discussion of the Related Art
Fluid distribution systems often include loop networks and/or branch networks with extended segments of piping or tubing through which flow is controlled using one or more valves. Typically, the valves are actuated by electric, pneumatic or hydraulic actuators which respond to control signals generated from a remote controller. Such fluid control systems frequently distribute cooling fluid through energy generation or energy management systems or are included as part of an automated fire control system as might be found aboard sea vessels.
In particular, shipboard firemain systems must be designed to operate in an automated manner since, at sea, there is seldom the time or manpower which can be brought to bear when considering the many necessary functions associated with operation of a vessel. Military ships must especially be self-sufficient and able to withstand battle damage anticipated during combat.
The U.S. Navy, among others, has been struggling to deal with the serious problems presented by shipboard fires as might be caused by a missile strike. After sustaining battle damage, it is imperative that the fluid handling systems aboard ship be controlled in a manner to isolate any damaged areas thereby preventing continuous flow from fluid supply sources to such damaged areas. Isolation of any ruptures in a reasonable time period also allows the intact portions of the systems to stabilize and restore normal fluid delivery operations through such portions.
Current technology associated with rupture or leak detection in fluid handling systems is based primarily in two areas, the utilization of hydraulic flow balance algorithms to detect fluid loss within a piping system and the utilization of acoustic signal characterization to determine leak conditions. Flow balance techniques utilize flow sensors distributed throughout the piping system to perform fluid mass balance evaluations within selected piping sections. Acoustic signal characterization techniques also distribute sensors throughout a piping system to xe2x80x9clistenxe2x80x9d for signals that provide an indication of a leak. Both techniques rely on communication between remote sensors and a central processor for identifying and effectively sealing a leak or rupture. Neither technique is practical for rapid and dependable detection of significant leaks or ruptures in the piping in situations where one or more sensors may be damaged and unable to provide detection information to the central processor. As a result, there is insufficient data to allow the processor to effectively isolate a rupture and restore intact portions of the system back to normal operating capabilities.
A more effective technique is needed for detecting and isolating ruptures automatically in fluid piping systems, particularly in systems having damaged sensors in addition to ruptured lines.
An object of the invention is to detect ruptures within a piping system without the need for communication between sensors and/or analysis of sensor data recorded in various remote locations throughout the system. Another object of the invention is to automatically and effectively isolate a detected rupture within a reasonable time period by sealing off the rupture from all fluid supply sources operating within the system thereby restoring a desired pressure and permitting fluid distribution within the non-ruptured sections of the piping system.
A further object of the invention is to provide a piping system having a plurality of valves within the system that are each capable of opening or closing based upon a detected characteristic of fluid in the immediate vicinity of each valve without the need for communicating with other valves or detecting characteristics of the fluid remote from each valve. Yet another object of the invention is to close valves within the system that were detected as being in fluid communication with a ruptured portion of the system in an order such that valves closest to the rupture and furthest from one or more fluid supply sources close first, thereby ensuring that the system is sealed off closest to the rupture while allowing as much of the intact system as possible to remain operational.
In order to meet the foregoing objectives, a method of detecting and isolating ruptures within a fluid piping system is provided, wherein the piping system has at least one fluid supply source and a plurality of open valves. The method includes continuously measuring a fluid characteristic at or near each valve, continuously detecting whether each valve within the piping system is on a rupture path within the piping system based upon a comparison of the measured fluid characteristic at or near each valve with a set point fluid characteristic for each valve, and opening or closing each valve based upon the outcome of the detection. Each valve will close or remain closed if the detection indicates that the valve is on a rupture path, whereas each valve will open or remain open if the detection does not indicate that the valve is on a rupture path. Additionally, under the rupture path logic method, open valves that are detected as being on a rupture path are closed in an order such that valves furthest from one or more fluid supply sources close prior to the closure of all other open valves on a rupture path.
A rupture detection and isolation fluid piping system is also provided including at least one fluid supply source and a plurality of valves. Each valve includes a first pressure sensor at or near the valve inlet, a second pressure sensor at or near the valve outlet, an actuator that automatically opens or closes the valve, and a processor in communication with both pressure sensors and the actuator. Each processor determines whether its respective valve is on a rupture path in the fluid piping system based upon a comparison of a fluid characteristic, obtained from pressure measurements at or near the first and second pressure sensors, with a set point fluid characteristic associated with its respective valve. Additionally, each processor opens or closes its respective valve via the actuator based upon the determination as to whether its respective valve is on a rupture path. A timer provided in each processor is activated upon a determination that its respective valve is on a rupture path thereby recording a rupture time for the valve, and each processor closes its respective valve when a rupture time exceeds a predetermined time delay for the valve. In order to ensure proper closure of the valves (i.e. valves closest to the rupture close before the closure of any other valve), the time delay for each valve is proportional to the distance between each valve and one or more fluid supply sources.
The methods and apparatus of the present invention incorporate valves having processors pre-programmed with rupture path logic steps for sensing and isolating damaged portions of fluid handling systems and restoring intact, undamaged sections to service, without intervention by shipboard personnel. In the methods of the present invention, the rupture is sensed and automatically isolated by cutting off damaged portions using only the information available at each valve. Use of global system information such as pre-damage configuration information from a remote supervisory or master control system preferably enhances system reliability and response time, but is not required for system operation, in the method of the present invention.
Each valve utilized in the invention includes first and second pressure sensors at or near the valve inlet and valve outlet, respectively, to measure a fluid characteristic, such as rupture resistance, in the fluid handling system pipe network. Optionally, each valve may also include a flow rate sensor for measuring the fluid flow rate at or near the valve. A fluid characteristic is determined from either the pressure readings or the pressure and flow rate readings. That fluid characteristic is compared to set point information stored by the processor and specific to each valve, and from such comparison a determination can be made as to whether the valve is on a rupture path. Valves closest to the rupture are closed first, and enough settling time is permitted so that other valves which had also been determined as being on a rupture path would detect any restored integrity to the fluid handling system. The rupture path logic incorporated within each valve therefore allows a valve to xe2x80x9cresetxe2x80x9d itself when applicable, i.e., to abort a xe2x80x9cclose valvexe2x80x9d command in the logic processing steps if the fluid characteristic at the valve no longer provides an indication that the valve is on a rupture path. Additionally, each valve in the system will continue sensing after a rupture has been detected and isolated. If a second rupture is detected, each valve will continue executing the rupture path logic steps whereupon the valve or valves closest to the rupture will close, thereby restoring the remaining undamaged portion of the fluid handling system to operation. In this way, the fluid system responds to changing circumstances without the need for human intervention.